# When a bottle of wine is opened, its hydrogen ion concentration, [H_3O^+]=4.1xx10^-4*mol*L^-1; what is its pH? How does the pH evolve after the wine is left to stand?

May 7, 2017

$p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right]$

#### Explanation:

And thus............when freshly opened $p H = - {\log}_{10} \left(4.1 \times {10}^{-} 4\right) = 3.39$.

(And in fact most wines have a $p H$ around this level.) See here for more detail on the definition of $p H$.

And later [H_3O^+]=0.0023*mol*L^-1; pH=2.64

The wine must not have been very good, because most wine is consumed within 12 hours after opening. What likely occurred is that the ethyl alcohol air-oxidized up to acetic acid, which is a carboxylic acid, and thus likely to have a lower $p H$ in aqueous solution. (Note that this oxidation is why we seal wine bottles with an air-tight cork/cap).

For the oxidation of ethyl alcohol to acetic acid we could write the equation:

$\text{H"_3"CCH"_2"OH(aq)" +"O"_2"(g)" rarr "H"_3"CCO"_2"H(aq)"+"H"_2"O(l)}$